Endoprosthesis having foot extensions

ABSTRACT

Endoprosthesis, such as a stent, includes at least one annular element defined by a first set of strut members interconnected to define apices proximate opposite sides of the annular element. The annular element further includes a foot extension extending between at least one pair of circumferentially-adjacent strut members. The foot extension has first and second foot portions extending circumferentially from corresponding ends of the circumferentially-adjacent strut members, and are contoured to provide at least two areas of flexure. The first and second foot portions are joined at a toe portion of the foot extension, and define a circumferentially-directed apex between the pair of circumferentially-adjacent strut members. Preferably, at least one or more additional annular elements, each defined by interconnected strut members, are provided. The annular elements are generally expandable between a delivery configuration and a deployed configuration. The annular elements are longitudinally aligned and connected at connection locations with connectors, wherein at least one of the connectors is constructed of a bio-absorbable material.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of application Ser.No. 11/228,621 which is a continuation-in-part of application Ser. No.10/992,976 which is a continuation-in-part of application Ser. No.10/430,644, the entireties of which are hereby incorporated byreference. The present application claims priority to U.S. ProvisionalApplication Ser. No. 60/659,499 filed Jun. 30 ,2005 the entirety ofwhich is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing anendoprosthesis for delivery and deployment within a body vessel of ahuman or animal. More particularly, the invention relates to a stentincluding at least one annular element having one or more footextensions for improved performance characteristics and at least oneradiopaque marker feature disposed in a portion of the endoprosthesis.

BACKGROUND OF THE INVENTION

Stents, grafts and a variety of other endoprostheses are well known andused in interventional procedures, such as for treating aneurysms, forlining or repairing vessel walls, for filtering or controlling fluidflow, and for expanding or scaffolding occluded or collapsed vessels.Such endoprostheses can be delivered and used in virtually anyaccessible body lumen of a human or animal, and can be deployed by anyof a variety of recognized means. One recognized indication ofendoprostheses, such as stents, is for the treatment of atheroscleroticstenosis in blood vessels. For example, after a patient undergoes apercutaneous transluminal coronary angioplasty or similar interventionalprocedure, an endoprosthesis, such as a stent, is often deployed at thetreatment site to improve the results of the medical procedure and toreduce the likelihood of restenosis. The endoprosthesis is configured toscaffold or support the treated blood vessel; if desired, theendoprosthesis can also be loaded with beneficial agent so as to act asa delivery platform to reduce restenosis or the like.

The endoprosthesis is typically delivered by a catheter delivery systemto a desired location or deployment site inside a body lumen of a vesselor other tubular organ. To facilitate such delivery, the endoprosthesismust be capable of having a particularly small cross profile to accessdeployment sites within small diameter vessels. Additionally, theintended deployment site may be difficult to access by a physician andoften involves traversing the delivery system through the tortuouspathway of the anatomy. It therefore is desirable to provide theendoprosthesis with a sufficient degree of longitudinal flexibilityduring delivery to allow advancement through the anatomy to the deployedsite.

Generally endoprosthesiss′ are constructed of multiple rings that areconnected either through a connection section or a connection element,wherein the number of connection sections or elements as well as thethickness of the struts that comprise the rings control the flexibilityof the endoprosthesis. Although it is not specifically known how muchvessel restenosis can be attributed to stent rigidity, it is know that areasonably stiff stent may injure the vessel during motion (i.e.pulsatile heart movement). Therefore, it is desirable to produce anendoprosthesis, which has good stiffness properties for deploymentwithin a vessel and wherein the stiffness properties of theendoprosthesis can be changed after deployment within a vessel.

Once deployed, the endoprosthesis should be capable of satisfying avariety of performance characteristics. The endoprosthesis should havesufficient rigidity or outer bias when deployed to perform its intendedfunction, such as opening a lumen or supporting a vessel wall.Similarly, the endoprosthesis should have suitable flexibility along itslength when deployed so as not to kink or straighten when deployed in acurved vessel. It also may be desirable to vary the rigidity orflexibility of the endoprosthesis along its length, depending upon theintended use. Additionally, it may be desirable for the endoprosthesisto provide substantially uniform or otherwise controlled coverage, e.g.,as determined by the ratio of the outer surface of the endoprosthesis tothe total surface of the vessel wall along a given length. For example,increased coverage may be desired for increased scaffolding, whereasdecreased coverage may be desired for side access to branch vessels.Control of the cross profile and length of the endoprosthesis upondeployment also is desirable, at least for certain indications.

Numerous designs and constructions of various endoprosthesis embodimentshave been developed to address one or more of the performancecharacteristics summarized above. For example, a variety of stentdesigns are disclosed in the following patents: U.S. Pat. No. 4,580,568to Gianturco; U.S. Pat. No. 5,102,417 to Palmaz; U.S. Pat. No. 5,104,404to Wolff; U.S. Pat. No. 5,133,732 to Wiktor; U.S. Pat. No. 5,292,331 toBoneau; U.S. Pat. No. 5,514,154 to Lau et al.; U.S. Pat. No. 5,569,295to Lam; U.S. Pat. No. 5,707,386 to Schnepp-Pesch et al.; U.S. Patent5,733,303 to Israel et al.; U.S. Pat. No. 5,755,771 to Penn et al.; U.S.Pat. No. 5,776,161 to Globerman; U.S. Pat. No. 5,895,406 to Gray et al.;U.S. Pat. No. 6,033,434 to Borghi; U.S. Pat. No. 6,099,561 to Alt; U.S.Pat. No. 6,106,548 to Roubin et al.; U.S. Pat. No. 6,113,627 to Jang;U.S. Pat. No. 6,132,460 to Thompson; and U.S. Pat. No. 6,331,189 toWolinsky; each of which is incorporated herein by reference.

An additional problem with existing endoprosthesis designs is thedifficulty in properly placing the endoprosthesis within a vessel priorto deployment of the endoprosthesis. Current endoprosthesis designs havethinner struts that utilize less radiopaque material and therefore donot appear as well under fluoroscopy. An attempt to address the reducedradiopacity is to include at least one marker band disposed on thedelivery device, wherein the marker band may be utilized to indicate anend of the endoprosthesis device or any length there along. Othermethods of increasing the radiopacity of an endoprosthesis include theaddition of radiopaque markers either disposed upon a surface of theendoprosthesis or within a retaining member associated withendoprosthesis. A shortcoming of present designs is that many are verydifficult to manufacture and therefore lead to increased costs. Also,due to size limitations of the radiopaque material used, the markers donot provide sufficient visibility for precise placement.

Another limitation of current endoprosthesis designs is theirunsuitability for materials with high elastic limits such asbioabsorbable polymers. The expansion of endoprosthesis devices such asstents generally relies on the plastic deformation of the stent materialand typical stent designs do not undergo enough strain during expansionto plastically deform bioabsorbable polymers. This can result inexcessive recoil of the stent and sub-optimal apposition of the stentagainst the vessel wall. Therefore, it is also desirable to provide astent design that enables expansion of the stent to a greater diameterwithout plastically deforming the stent material.

Although the various designs for endoprostheses that have been developedto date may address one or more of the desired performancecharacteristics, there a remains need for a more versatile design for anendoprosthesis that allows improvement of one or more performancecharacteristics without sacrificing the remaining characteristics.

SUMMARY OF THE INVENTION

The purpose and advantages of the present invention will be set forth inand are apparent from the description that follows, as well as will belearned by practice of the invention. Additional advantages of theinvention will be realized and attained by the methods and devicesparticularly pointed out in the written description and claims hereof,as well as from the appended drawings.

To achieve these and other advantages in accordance with the purpose ofthe invention, as embodied herein and broadly described, the inventionincludes an endoprosthesis for delivery and deployment in a body lumen.The endoprosthesis includes at least one annular element defined by afirst set of interconnected strut members, wherein each strut member hasa first end and a second end. Preferably, the first end of selectedcircumferentially-adjacent strut members are interconnected to defineapices proximate a first longitudinal side of the first annular elementand the second end of selected circumferentially-adjacent strut membersare interconnected to define apices proximate a second longitudinal sideof the first annular element. The annular element further includes afoot extension extending between a pair of circumferentially adjacentstrut members. The foot extension has a first foot portion extendingcircumferentially from the first end of one of the circumferentiallyadjacent strut members of the pair and a second foot portion extendingcircumferentially from the first end of the other of thecircumferentially-adjacent strut members. The first and second footportions are joined at a toe portion of the foot extension, andgenerally define an apex between the pair of circumferentially adjacentstrut members.

Preferably, the endoprosthesis of the invention further includes asecond annular element defined by a second set of interconnected strutmembers, wherein each strut member of the second annular element alsohas a first end and a second end. Circumferentially adjacent strutmembers are interconnected to define apices on opposite sides of thesecond annular element. The first annular element and the second annularelement are aligned longitudinally adjacent to each other along alongitudinal axis and connected to each other at least one connectionlocation. The second annular element also can include a foot extension.Additional annular elements also can be provided.

The annular elements are generally expandable between a deliveryconfiguration and a deployed configuration. Each annular element can bedefined as a continuous closed ring, or as a coiled sheet or the like.Preferably, each strut member is a straight member, aligned to besubstantially parallel with the longitudinal axis of the endoprosthesiswhen in the delivery configuration. Selected strut members can have auniform width or can have varied width, such as a continuous taper orincreased midsection width between the opposite ends of the strutmember. Alternatively, selected strut members may include generallyopposed projections that undergo relative motion during stent expansion,but that interfere with each other following expansion, therebypreventing recoil of the expanded stent to a significantly lowerdiameter. The apices on either side of each annular element that are notdefined by a foot extension can have a V-shape, an arcuate shape, oranother shape as desired. For example, the apices may have an arcuatestructure with at least two segments, wherein the area defined betweenthe segments increases during stent expansion and whereby the arcuatestructure is modified to support the strut members in a second stableposition.

The foot extension is contoured to provide at least two areas offlexure, and extends circumferentially at an angle relative to thelongitudinal axis of the annular element. The foot extension can includestraight portions, curved portions or combinations thereof to define anankle portion, a toe portion, a base portion and a heel portion. Thebase portion can be a straight member, or contoured as a V-shape or thelike. In a preferred embodiment, the foot extension has an average widthgreater than that of the remaining strut members of the annular element.With the foot extension located between longitudinally adjacent annularelements, the base portion of the foot extension generally faces thelongitudinally adjacent annular element.

Preferably, the connection location between the longitudinally adjacentannular elements includes the foot extension. By providing theconnection location at the base portion of the foot extension, theapices proximate a side of the first annular element generally can bearranged circumferentially out of alignment, or less than 180 degreesout of phase, with the apices proximate a facing side of the secondannular element. The connection location can be defined by anoverlapping pattern between the longitudinally adjacent annularelements, such as the base of a foot extension on one annular elementand a corresponding apex on the other annular element. Alternatively,the connection location can include a connector extending between theannular elements. The connector can be a straight member or a shapedmember, with opposites ends circumferentially either in or out ofalignment, as desired. In a preferred embodiment, the connector has anL-shape, with one leg longer than the other leg. It is furthercontemplated that the connector may be partially or fully constructed ofa bioabsorbable material, wherein after deployment within a vessel, thebioabsorbable component of the connector is absorbed thereby changingthe stiffness of the endoprosthesis. In a preferred embodiment, aplurality of connection locations are provided between the adjacentannular elements, with a foot extension provided at some or all of theconnection locations. The plurality of foot extensions can all extend inthe same circumferential direction, or can be arranged to extend inopposing circumferential directions.

A radiopaque material preferably is incorporated in at least a portionof the endoprosthesis. For example, at least one of the annular elementscan comprise radiopaque material. Alternatively, radiopaque markers canbe attached to at least one of the annular elements, or the annularelements can be formed of radiopaque material. As another example, atleast one of the annular elements can be formed with a first layer ofbase material and a second layer of radiopaque material.

In accordance with the present invention there is provided anendoprosthesis device for delivery in a body lumen, comprising athin-walled, generally tubular member having open ends with a firstdiameter and a second diameter; and at least one marker elementconnected to at least one end of the thin-walled generally tubularmember, the at least one marker comprising a marker housing and a rivet,the rivet extending generally beyond an outer surface and an innersurface of the substantially tubular member.

In accordance with the present invention there is provided a method ofmanufacturing an endoprosthesis device, comprising the steps of (a)forming an endoprosthesis for delivery in a body lumen (b) smoothingsurfaces of the endoprosthesis by media blasting (c) polishing thesurfaces of the endoprosthesis with an electropolishing process (d)disposing a radiopaque marker within an opening formed within astructure of an endoprosthesis device (e) applying a force to saidmarker, thereby forming two heads on the marker, wherein each of theheads extends beyond and inner and an outer surface of theendoprosthesis device. The method may further include the step ofpassivation, either prior to placing the marker within the opening orafter placement or any combination thereof.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and are intended toprovide further explanation of the invention claimed.

The accompanying drawings, which are incorporated in and constitute partof this specification, are included to illustrate and provide furtherunderstanding of the device of the invention. Together with thedescription, the drawings serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a representative embodiment, in planar format, of anendoprosthesis in accordance with the invention.

FIG. 1 b illustrates an exemplary embodiment of a connector inaccordance with the present invention.

FIGS. 2 a through 2 k show detail views, in planar format, of variousexemplary foot extensions in accordance with the present invention.

FIGS. 3 through 9 show representative embodiments of the presentinvention in planar format, each of an endoprosthesis having annularelements connected at a plurality of connection locations withoutconnectors.

FIGS. 10 and 11 illustrate alternative embodiments of the presentinvention, wherein a marker housing and a marker are shown to beassociated with the endoprosthesis.

FIG. 12 is an exemplary embodiment of a marker having a pre-formed firsthead formed thereon in accordance with the process according to thepresent invention.

FIG. 13 is a side view of an eyelet of an endoprosthesis having a markerdisposed therein in accordance with the process of the presentinvention.

FIG. 14 is a side view of a fixture for forming markers within eyeletsin accordance with the present invention

FIG. 15 is an end view of a portion of the marker forming fixture ofFIG. 14.

FIG. 16 is a top view of a portion of the marker forming fixture of FIG.14.

FIG. 17 is an isometric view of a holding fixture for insertingradiopaque markers into an endoprosthesis.

FIG. 18 is a top view of a portion of the holding fixture illustratingthe holding jaws in an open position.

FIG. 19 is a top view of a portion of the holding fixture illustratingthe holding jaws in a closed position.

FIGS. 20 and 21 a through 21 d are detail views, in planar format,showing various embodiments of overlapping patterns of adjacent annularelements defining connection locations.

FIG. 22 shows a representative embodiment, in planar format, of anendoprosthesis configured to have varied characteristics along itslength.

FIGS. 23 a through 23 f respectively show a preferred embodiment of aself-expanding stent in accordance with the present invention, (a) inplanar format, (b) in a front-half side view as cut and polished from atube, (c) in a front-half side view of a delivery configuration, (d) ina front-half side view of a deployed configuration, (e) in a perspectiveview of a deployed configuration, and (f) in a side view as deployed ina curved vessel.

FIGS. 24 a through 24 f respectively show a preferred embodiment of aballoon expandable stent in accordance with the present invention, (a)in planar format, (b) in a front-half side view as cut and polished froma tube, (c) in a front-half side view of a delivery configuration, (d)in a front-half side view of a deployed configuration, (e) in aperspective view of a deployed configuration, and (f) in a side view asdeployed in a curved vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, an endoprosthesis is providedfor delivery within a body lumen of a human or animal. Theendoprosthesis can include, but is not limited to, stents, grafts,valves, occlusive devices, trocars, aneurysm treatment devices, or thelike. The endoprosthesis of the present invention can be configured fora variety of intralumenal applications, including vascular, coronary,biliary, esophageal, urological, gastrointestinal or the like.

Generally, the endoprosthesis of the present invention includes a firstset of interconnected strut members defining a first annular element,wherein each strut member of the first annular element include a firstend and a second end. The endoprosthesis also includes a foot extensionextending between a pair of circumferentially adjacent strut members. Asdescribed further below, the foot extension has a first foot portionextending circumferentially from the first end of one of thecircumferentially-adjacent strut members and a second foot portionextending circumferentially from the first end of the other of thecircumferentially-adjacent strut members. The first and second footportions are joined at a toe portion of the foot extension.

Preferably, and as embodied herein, the endoprosthesis further includesat least a second set of interconnected strut members defining a secondannular element. The endoprosthesis can include additional annularelements defined by interconnected strut members as desired or needed.Each annular element generally defines a structure extendingcircumferentially about a longitudinal axis. The cross profile of eachannular element preferably is at least arcuate, and more preferablyeither circular or spiral, although alternative cross profiles, such asrectilinear or the like, can be used if desired.

The first annular element is aligned longitudinally adjacent to thesecond annular element along the longitudinal axis, and connected toeach other at at least one connection location. Preferably, the firstand second annular elements generally define a tubular structure. Forexample, each annular element can define a continuous closed ring suchthat the longitudinally aligned annular elements form a closed tubularstructure having a central longitudinal axis. Alternatively, eachannular element can define an open ring such that a rolled sheet or opentubular type structure is defined by the annular elements. Furthermore,each annular element can define a 360-degree turn of a helical pattern,such that the end of one annular element can be joined with thecorresponding end of a longitudinally adjacent annular element to definea continuous helical pattern along the length of the endoprosthesis.

Each strut member of the annular elements includes a first end and asecond end. The strut members of each annular element are disposedcircumferentially adjacent to each other, and interconnected so as todefine an expandable structure. For example, and with reference to theclosed tubular structure above, circumferentially-adjacent strut membersof each annular element can be interconnected, either directly orindirectly, in an end-to-end format to define a continuous ring having agenerally circular cross profile. By altering the angle or distancedefined between circumferentially adjacent strut members, the tubularstructure can be radially expanded between a delivery configuration anda deployed configuration. As discussed in detail below, the expandablestructure can be expanded by the application of an external force, suchas by a balloon, or by a change in delivery conditions, such as anincrease in temperature or the removal of a restraint, so as to allowthe structure to self expand. With reference to FIG. 1 a, for purpose ofillustration and not limitation, a representative embodiment of anendoprosthesis 100 of the present invention in a deployed configurationis depicted in a planar format for clarity. As shown in FIG. 1 a, theendoprosthesis includes a plurality of annular elements 10 alignedlongitudinally adjacent to each other along a longitudinal axis 15.Although only one annular element need be provided in accordance withthe invention, it is preferable that the endoprosthesis includes aplurality of annular elements 10, depicted herein for purpose ofillustration by at least a first annular element 10′ and a secondannular element 10″.

Each annular element includes a set of interconnected strut members 20,which are disposed circumferentially about longitudinal axis 15. Eachstrut member has a first end 22′ and a second end 22″, referencedgenerally as end 22. The first end 22′ of selectedcircumferentially-adjacent strut members 20 are interconnected to defineapices 30 proximate a first longitudinal side 12 of each annular element10, and the second end 22″ of selected circumferentially-adjacent strutmembers 20 are interconnected to define apices 30 proximate a secondlongitudinal side 14 of the annular element. In this manner, eachannular element 10 can be expanded to a deployed configuration as shownin FIG. 1 a by altering or “opening” the angle defined betweencircumferentially-adjacent strut members 20. It also is recognized inthe embodiment of FIG. 1 a that circumferentially-adjacent apices 30 oneach side 12, 14 of the annular element 10 are spaced apart by acircumferential distance D, such that each annular element is expandedby increasing the distance D between circumferentially-adjacent apices30. At any given condition between the delivery configuration and thedeployed configuration, the distance D can be balanced or constant fromone set of circumferentially adjacent apices to the next, or can bevaried if desired.

As shown in FIG. 1 a, certain apices 30 on each side of the annularelement 10 can be defined by interconnecting corresponding ends 22 ofcircumferentially-adjacent strut members directly together to form azig-zag pattern of alternating V-shapes when deployed. Alternatively, anapex member can be provided between the corresponding ends of adjacentstrut members to form a contoured apex, such as by using a straight apexmember to form a flat apex as disclosed in U.S. Pat. No. 6,113,627 toJang, or a curved apex member to form an arcuate apex as disclosed inU.S. Pat. No. 5,514,154 to Lau.

In the representative embodiment of FIG. 1 a, the strut members 20 ofeach annular element 10 are interconnected with adjacent strut members20 to form a continuous closed ring, such as depicted more clearly inFIGS. 23 e and 24 e. As previously noted, however, each annular elementcan define an open ring to form a rolled sheet or open tubular typestructure as described further with regard to FIG. 3, or can defineadjacent turns of a continuous helical pattern as described.

FIG. 1 a also depicts each strut member 20 of the annular element 10 asa straight member. Preferably, when in the delivery configuration, thestraight strut members 20 are generally aligned parallel with thelongitudinal axis 15, as well as with each other, as shown for examplein FIGS. 23 c and 24 c. Although not shown, alternative strut membershapes can be used in addition to or in lieu of the straight strutmembers, such as L or V-shaped strut members or the like as is known inthe art. Also, the number of strut members included in each annularelement will depend upon the size and desired characteristics of theendoprosthesis. For example, a greater number of strut members andinterconnecting apices can be provided for increased coverage of thevessel wall by the endoprosthesis or increased cross profile of theendoprosthesis in the deployed configuration.

Similarly, the radial bias or rigidity of each annular element can becontrolled or varied by altering the shape or size of the strut members.For example, radial bias or rigidity of an annular element, whendeployed, generally can be increased by decreasing the length or bymodifying the cross sectional profile of selected strut members of theannular element. It therefore is possible to provide an endoprosthesisin accordance with the present invention having varied radial bias orrigidity along its length by providing one annular element with a radialbias or rigidity that is different from the radial bias or rigidity ofanother annular element as shown in FIG. 22 and described further below.In a similar manner, it is possible to provide an endoprosthesis havinga tapered or flare shape formed of adjacent annular elements havingdifferent cross profiles when in the deployed configuration but similaror uniform radial bias or rigidity along its length.

Further in accordance with the present invention, and as previouslynoted, at least one annular element includes a foot extension extendingbetween at least one pair of circumferentially-adjacent strut members.The foot extension can thus define an apex between the pair ofcircumferentially-adjacent strut members of the annular element. Thefoot extension includes a first foot portion extending circumferentiallyfrom an end of one of the adjacent strut members and a second footportion extending circumferentially from a corresponding end of theother of the circumferentially-adjacent strut members. In combination,the first and second foot portions generally define an ankle portion, atoe portion, a base portion and a heel portion of the foot extension,which in combination define a generally circumferentially directed apex.

With reference to the exemplary embodiment of FIG. 1 a, for illustrationand not limitation, foot extension 40 extends between a pair 9 ofadjacent strut members 20 of each annular element 10. As depicted forpurpose of illustration, the foot extension 40 includes a first portion41 extending circumferentially from an end 22 of one of the adjacentstrut members 20, and a second portion 43 extending circumferentiallyfrom the corresponding end 22 of the other of the adjacent strut members20. The juncture of the first and second foot portions 41, 43 defines acircumferentially extending toe portion 48 of the foot extension 40.Similarly, and for purpose of discussion and not limitation, FIG. 1ashows that an ankle portion 44 is defined proximate the juncture of thefirst foot portion 41 with one of the circumferentially-adjacent strutmembers 20, and that a heel portion 42 is defined proximate the junctureof the second foot portion 43 with the other of thecircumferentially-adjacent strut members 20. The toe portion 48 extendsin a first circumferential direction a distance greater than the heelportion 42 of the foot extension 40 extends in an oppositecircumferential direction. In the embodiment of FIG. 1 a, the entiretyof the foot extension 40 extends in the circumferential direction of thetoe portion 48. Furthermore, at least one of the first and second footportions 41, 43 defines a base portion 46 at or proximate to thecorresponding side 12 or 14 of the annular element 10. Defined generallywithin the boundary of the first and second portions 41, 43 is an openfoot region 49 (see also, FIG. 2 a).

With reference again to FIG. 1 a, a plurality of connectors 60 areprovided to connect adjacent annular elements 10 at a plurality ofconnection locations 50. Each connection location 50 of FIG. 1 aincludes a foot extension 40 of one annular element and an apex 30 ofanother annular element, with a connector 60 having opposite ends 62connected therebetween. If desired, however, the connection location 50can extend from a foot extension to a foot extension, or from an apex toan apex, or to a strut member of one or both annular elements ifdesired. As embodied in FIG. 1 a, each foot extension 40 generally has acircumferentially elongated base portion 46 facing an adjacent annularelement 20. With a connector 60 extending longitudinally from the baseportion 46 of a foot extension 40 to an apex 30, thelongitudinally-adjacent apices 30 of adjacent annular elements arecircumferentially out of alignment. The foot base portions 46 at thelongitudinal ends 102, 104 of the endoprosthesis 100 face outward fromthe remainder of the structure. Preferably, one or more foot extensionsat either end 102, 104 of the endoprosthesis includes an area thatundergoes minimal deformation or strain, such as the base portion 46,when expanded to the deployed configuration. A wire or strip ofradiopaque material can be wrapped around or otherwise secured to thisarea of minimal strain so as to act as a radiopaque marker 120 forimaging purposes. Alternatively, a marker tab or eyelet can be attachedat one or both ends of the endoprosthesis as described in detail withreference to FIGS. 10 and 11, below. For simplicity and clarity, eachconnector depicted in FIG. 1 a is a straight member. It is recognized,however, that the connector can be contoured or shaped to increaselongitudinal flexibility if desired. Similarly, the connectors need notextend parallel to the longitudinal axis, but can be aligned diagonallyor helically such that the ends of the connector are circumferentiallyoffset.

A variety of design alternatives for different endoprosthesisembodiments can be achieved by selectively combining the various aspectsof the present invention. For purpose of illustration and notlimitation, a number of exemplary embodiments including the combinationof connectors with foot extensions of the present invention are depictedin planar format in FIGS. 3-11. As with the embodiment of FIG. 1 a, theconnectors are depicted as straight members for clarity and simplicity,but any connector configuration can be used as desired.

As previously described herein, the annular elements are preferablyunitarily constructed from a sheet member or a tubular member, whereinthe connectors 60 are unitarily constructed along with the annularelements utilizing known construction methods such as laser cutting oretching. In accordance with an alternative embodiment, the annularelements 10 may be constructed individually, either from sheet materialor tubular material as described herein, wherein the connectors 60 aredisposed at connection locations 50 thereby forming an endoprosthesishaving more than one annular member.

Referring now to FIG. 1B, there is shown an alternative embodiment of aconnector 60′ in accordance with the present invention. In thisalternative embodiment, the connectors 60′ may be constructed fully of abio-absorbable material, partially of a bio-absorbable material or of amaterial different than that of the annular elements 10. By forming theconnectors 60′ of a bio-absorbable material, mechanical properties ofthe endoprosthesis can be tuned or adjusted accordingly. For example, agreater number of connectors 60′ may be utilized to connect the annularrings 10 together, thereby providing greater column strength fordelivery of the endoprosthesis. Once the endoprosthesis has been placedwithin a vessel or artery, the connectors 60′ would then be absorbedthereby allowing each of the annular rings to move independent of oneanother. By having each of the annular rings 10 able to moveindependently of one another the flexibility of the endoprosthesis isgreatly improved which may lead to a reduction of restenosis. It isfurther contemplated that individual connectors 60′ may be constructedof different bio-absorbable materials, wherein pairs of connectors 60′or individual connectors 60′ may be absorbed at different rates.Additionally, pairs of connectors 60′ or single connectors 60′ may beconstructed of non-absorbable materials, wherein the absorbableconnectors provide column strength during delivery of the endoprosthesisand the non-absorbable connectors provide connection points between theindividual annular rings 10 thereby preventing the annular rings 10 frommoving independently, though still providing increased flexibility ofthe expanded endoprosthesis from the reduction of connectors 60′.

Examples of bio-absorbable materials of which the connectors 60′ may beconstructed of may be an inert material, a beneficial agent, or acombination of the two. An example of a suitable beneficial agent isdescribed in U.S. Pat. No. 6,015,815 and U.S. Pat. No. 6,329,386jentitled “Tetrazole-containing rapamycin analogs with shortenedhalf-lives”, the entireties of which are herein incorporated byreference. It shall be understood that more than one beneficial agentmay be combined with one or more inert materials to form the connectors60′. Examples of suitable bio-absorbable materials include Polygycolicacid (PGA), Polyhydroxybutyric acid, PolyL-Lactic acid (PLLA),Polydilactidel glycolide, Polydilactid acid, PolyDL lactide-co-gycolide.

Further still, as shown in FIG. 1 b there is yet an alternativeembodiment of the connectors 60′ in accordance with the presentinvention. As shown in FIG. 1 b, the connectors 60′ are provided toconnect adjacent annular elements 10 at a plurality of connectionlocations 50. Each connection location 50 of FIG. 1 a includes a footextension 40 of one annular element and an apex 30 of another annularelement, with a connector 60 having opposite ends 62 connectedtherebetween. If desired, however, the connection location 50 can extendfrom a foot extension to a foot extension, or from an apex to an apex,or to a strut member of one or both annular elements if desired. Asshown in FIG. 1 b, the connector 60″ is partially constructed having ametallic member 60 a′ and a bio-absorbable member 60 b′, wherein thebio-absorbable member 60 b′ is disposed about the metallic member 60 a′.By producing the connector 60″ in this manner, the column strength ofthe endoprosthesis is increased, thereby aiding in tracking anddeployment, wherein the bio-absorbable material is then absorbed afterdeployment and expansion, thereby reducing the column strength of theendoprosthesis.

It may be desirable to choose a bio-absorbable material or materialsthat can be selectively activated to be made absorbable. For example,after expansion of the endoprosthesis within a vessel or artery, anactivating agent may be delivered to the site of expansion, whereby thebio-absorbable connectors 60′ are activated thereby becoming absorbable.By making the connectors 60′ selectively absorbable, the stiffness andcolumn strength of the endoprosthesis can be varied or altered asdesired after implantation. For example, if greater flexibility isdesired more connectors may be activated to be absorbed.

It is further contemplated that the bio-absorbable connectors inaccordance with the present invention may be configured to be responsiveto radio-frequency (RF) energy or ultrasonic energy, wherein thebio-absorbability of the connectors would be altered in response toapplied energy. For example, the absorption rate may be increased ordecreased in response to the applied energy; additionally it iscontemplated that the connectors may be disconnected from the rings inresponse to applied energy. Suitable RF devices that may be utilizedwith the present invention include “The Crosser” from FlowCardia or the“Resolution” from OmniSonics Medical Technologies, Inc.

Still further, it is contemplated that the alternative embodiments ofthe connectors 60 in accordance with the present invention as describedabove may be constructed either partially or fully of a non-absorbablebio-compatible material. Such a connector configuration would allow ofthe use of multiple materials for construction of the individual annularrings. For example, a ring constructed of nitinol could be coupled witha ring constructed of a bio-absorbable material or anotherbio-compatible material, thereby enabling the formation of a compositeendoprosthesis.

A variety of configurations can be used for the foot extension inaccordance with the present invention. For purpose of illustration andcomparison with the foot extension of FIG. 1 a, exemplary embodiments ofvarious alternative foot extension configurations are depicted in FIGS.2 a through 2 f.

For example, the foot extension of the invention generally extends fromthe pair of circumferentially adjacent strut members circumferentiallyat an angle relative to a line parallel to the longitudinal axis of theannular element. FIG. 1 ashows a foot extension generally extendingcircumferentially at an angle of about 90 degrees relative to thelongitudinal axis 15. However, the foot extension can be configured toextend circumferentially at an angle of less than 90 degrees relative tothe longitudinal axis, as shown for example in FIG. 2 a.

Additionally, FIG. 1 a shows a foot extension 40, wherein the first footportion 41 and the second foot portion 43 are generally parallel,straight elongate portions joined by curved portions. Particularly, thebase portion 46 is defined by a generally straight portion and each ofthe toe portion 48, the ankle portion 44 and the heel portion 42 isdefined by a curved portion. Each portion of the foot extension 40, aswell as each of the circumferentially-adjacent strut members 20, has asubstantially uniform width W and thickness in the embodiment of FIG. 1a. In this manner, the circumferentially-adjacent strut members 20 willbe substantially parallel to the longitudinal axis 15 and to each other,and region 49 will be substantially closed when in the deliveryconfiguration. As depicted in FIG. 1 a, the foot extension 40 will thusgenerally define at least two areas of flexure between the pair ofcircumferentially-adjacent strut members 20; that is, one at the heelportion 42 and one at the ankle portion 44. An additional, oralternative, area of flexure can be defined at the toe portion 48 ifdesired to facilitate further expansion between the pair ofcircumferentially-adjacent strut members 20, such as to define a threepoint hinge configuration.

FIG. 2 a depicts a preferred embodiment of a foot extension similar tothat of FIG. 1 a. As previously noted, however, the foot extension 40 ofthis embodiment extends circumferentially at an angle α less than 90degrees relative to the longitudinal axis 15. Additionally, the firstand second foot portions 41, 43 are generally parallel but spaced apartto define a relatively more open region 30 than that of the footextension of FIG. 1 a. To control expansion of the annular element, thewidth of the foot extension and circumferentially-adjacent strut memberscan be varied accordingly. For example, and as previously noted,circumferentially-adjacent apices along each side of the annular element10 are spaced apart by a circumferential distance D, wherein thedistance D generally increases as the annular element is expanded. It isoften desirable to balance an annular element so as to expand uniformly,wherein the distance D increases a similar amount and at a similar ratebetween each pair of circumferentially-adjacent apices. Due to theincreased flexure facilitated by the foot extension similar of FIG. 1 a,the distance Df between the circumferentially-adjacent apices located atthe end of the pair 9 of circumferentially-adjacent strut members 20opposite the foot extension 40 can increase to an extent or at a rategreater than the distance Da between other circumferentially-adjacentapices of the annular element. By providing the first and second footportions 41, 43 of the foot extension with an average width greater thanthe average width of the circumferentially-adjacent strut members 20, asshown in FIG. 2 a, the expansion between the circumferentially-adjacentapices 30 can be controlled or even balanced if desired. For example,and as shown in FIG. 2 a, the first and second foot portions 41, 43 canbe provided with a substantially constant width. Alternatively the firstfoot portion 41 can be provided with a width WI different than that W2of the second foot portion 43.

As previously noted with regard to the exemplary embodiment of FIG. 1 a,the circumferentially-adjacent strut members 20 and the differentportions of the foot extension 40 can be provided with a substantiallyuniform width and thickness throughout. If the foot extension isprovided with an increased width, it may be desirable or necessary todistribute stress or eliminate stress concentrations in the pair ofcircuniferentially-adjacent strut members 20. As embodied in FIG. 2 a,at least one or both strut member 20 of the pair 9 ofcircumferentially-adjacent strut members can be provided with a variedwidth. For example, and as shown in FIG. 2 a, each strut member of thepair 9 of circumferentially-adjacent strut members can be tapered from afirst width W′ substantially similar to or even greater than that of thefoot extension at the first end 22′ of the strut member to a secondwidth W″ substantially similar to or even greater than that of theadjacent strut member 20 connected at the second end 22″.

To further control expansion of the annular element, selected apicesalong the same longitudinal side 12, 14 of the annular element 10 as thefoot extension also can be modified. For example, an apex 30 can berelaxed by reducing its width to facilitate greater expansion, orstiffened by increasing its width to facilitate less expansion. As shownin FIG. 2 a, the width of selected apices 30 rw are reduced to relax theapex 30 and thus control, such as balance, expansion of the annularelement as needed or desired.

Furtherrnore, selected apices on the same side of the annular element asthe foot extension can be configured to accommodate additional features.For example, and in accordance with another aspect of the presentinvention, it is desirable to enhance retention of a balloon expandableendoprosthesis on a balloon delivery system. As shown in FIG. 2 a, thefoot extension 40 extends in a first circumferential direction, and acircumferentially-adjacent apex 30 a is located proximate the footextension 40 in the first circumferential direction. When in thedelivery configuration, this circumferentially-adjacent apex 30 a islongitudinally aligned with, and preferably can substantially contact,the toe portion 48 of the foot extension so as to define a gap G betweenthe circumferentially-adjacent strut members 20. Balloon material of thedelivery system thus can be captured within this gap G, during crimpingor through known heat treatment techniques, to enhance stent retentionon a balloon. Additionally, or alternatively, a gap can be definedwithin an enlarged region 49 of the foot extension 40 for similar stentretention purposes if desired.

FIG. 2 b depicts yet another foot extension configuration in accordancewith the invention. The first foot portion 41 of the foot extension 40is generally angled relative to the second foot portion 43, rather thanaligned in parallel as shown in FIG. 1 a. Additionally, the second footportion 43 is generally V-shaped to define a base portion 46 extendingsubstantially perpendicular to the longitudinal axis, but with a moreangular heel portion 42 than that of FIG. 1 a. In this manner, the firstand second foot portions define an enlarged open region 49 relative tothat of FIG. 1 a. As with FIG. 2 a, the embodiment of FIG. 2 b includesa foot extension 40 having an increased average width and taperedcircumferentially-adjacent strut members, as well as alongitudinally-aligned apex 30 a circumferentially adjacent to the toeportion 48 of the foot extension 40 for enhanced retention on a balloondelivery system.

FIG. 2 c depicts an alternative preferred embodiment of the footextension of the present invention. The foot extension 40 of thisembodiment is provided with a generally rectilinear configuration,including a first foot portion 41 extending from the ankle portion 44 tothe toe portion 48 of the foot extension, and a second foot portion 43extending from the heel portion 42 to the toe portion 48. Particularly,the second foot portion defines a contoured base portion 46, such as agenerally V-shape including a first portion 46′ and a second portion46″. In this manner, the foot extension can be configured to provide anadditional area of flexure for expansion of the annular element ifdesired, as well as to define a connection location forlongitudinally-adjacent annular elements as described further below.

As with the embodiments of FIGS. 2 a and 2 b, the first and second footportions 41, 43 of FIG. 2 c are provided with an increased width tostiffen the apex defined by the foot extension 40, and thus control, andmore preferably, balance expansion of the annular element 10. Forexample, in one preferred embodiment, the width WI of the first footportion 41 and the width W2′ of the first portion 46′ of the V-shapedbase portion are equal to each other, but different than the width W2″of the second portion 46″ of the V-shaped base portion. Unlike theembodiment of FIGS. 2 a and 2 b, which are particularly advantageous incombination with a balloon delivery system, the embodiment of FIG. 2 cdoes not include a longitudinally-aligned apex circumferentiallyadjacent the toe portion of the foot extension. Rather, and asrecognized from FIG. 2 c, at least the apex 30 a locatedcircumferentially proximate the toe portion 48 of the foot extension 40is positioned longitudinally so as to mate with the foot extension whenin the delivery configuration. For example, and as shown in FIG. 2 c,this can be accomplished by providing at least one of the strut members20 of the pair 9 of circumferentially-adjacent strut members with alength greater than the length of the remaining strut members of theannular element. The mating configuration between the foot extension 40and the circumferentially adjacent apex 30 a facilitates a reduced crossprofile of the annular element 10 when in the delivery configuration.This embodiment is particularly advantageous for an endoprosthesis to bedelivered within extremely small vessels, such as certain coronary orneurovascular vessels, or for an endoprosthesis that can be containedwithin a sheath during delivery, such as a self-expanding stent.

FIG. 2 d is a enlarged detail view of a more rounded version of a footextension similar to that of FIG. 2 c, which is depicted with dashedlines for purpose of comparison. Particularly, FIG. 2 d demonstrates theused of more rounded contours to shift or eliminate stressconcentrations that may occur during expansion.

FIG. 2 e depicts another alternative embodiment of a foot extension thepresent invention, which incorporates the mating configuration of thefoot extension and the circumferentially adjacent apex as described withregard to FIG. 2 c. Unlike the embodiment of FIG. 2 c, however, thestrut members 20 connected to the circumferentially adjacent apex 30 aare provided with a length less than that of the remaining strut membersso as to accommodate the desired mating relationship between the apex 30a and the foot extension 40. Furthermore, FIG. 2 e shows that at leastthe circumferentially adjacent apex 30 a is relaxed, such as byproviding a reduced width, to open at a greater angle and thuscompensate for the decrease of the distance D that would otherwiseresult during expansion due to the reduced length of the correspondingstrut members 20. As previously described, expansion of the annularelement 10 thus can be controlled, and more preferably, balanced. Thestrut members 20 having a reduced length and thecircumferentially-adjacent apex 30 a also can be provided with a reducedwidth if desired as shown in FIG. 2 e.

Referring now to FIG. 2 f there is shown yet another embodiment of afoot extension in accordance with the present invention, as shown inFIG. 2 f, the foot extension 40′ includes a first foot portion 41extending from the ankle portion 44 to the toe portion 48 of the footextension, and a second foot portion 43 extending from the heel portion42 to the toe portion 48, wherein a modulator member 47 is disposedadjacent the ankle portion 44 and the heel portion 42. The modulatormember 47 couples two adjacent strut members as shown. The modulatormember 47 may be formed having a width similar to the adjacent strutmembers or may be constructed having a width that is greater than orless than the adjacent strut members or foot extension. Additionally,the modulator member 47 may be constructed as a linear member or as amember having an arc length, wherein upon expansion of theendoprosthesis from a contracted or crimped profile to an expandedprofile the modulator member 47 may be designed to limit the expansiondiameter of the endoprosthesis by redistributing stress/strain away fromthe foot portion of the endoprosthesis, thus, resulting in more uniformexpansion/contraction of the endoprosthesis. Additionally, as shown inFIG. 2 f, the placement of the modulator member 47 creates a well oropen space 49 defined by the foot portion 40′ and the modulator 47. Itis contemplated that the space 49 may be utilized as a reservoir for abeneficial agent such as those described herein and in detail below.Additionally, it is contemplated that at least one radiopaque markermember may be placed into at least one of the spaces 49 as described ingreater detail below with regard to the methods and processes describedbelow.

The modulator 49 may be constructed of a bio-absorbable material in asimilar manner to the connector 60′ as previously described.Additionally, the modulator may have a composite construction wherein aportion of the modulator 49 is constructed of the same material as theendoprosthesis and the second portion is a different material. Thesecond material may be a bio-absorbable material such as thosepreviously described, or a beneficial agent, or a non-absorbablebio-compatible material.

Referring now to FIGS. 2G though 2K there is shown an alternativeembodiments of the modulator component in accordance with the presentinvention. As shown in FIGS. 2G and 2H the modulator is constructedhaving bistable properties. As shown in FIGS. 21 through 2K there isshown a multi-piece modulator, wherein the multiple pieces of themodulator function together in a manner described below.

Referring now to FIGS. 2G and 2H there is shown an alternativeembodiment of the modulator disposed between the apices interconnectingcorresponding ends of circumferentially adjacent strut members. Themodulator can be provided having an arcuate structure with at least twosegments 502, 504 defining an internal area 506 therebetween. The firstsegment 502 is generally wider than the second segment 504 making thesecond segment less resistant to flexure. Each segment has a first and asecond end. Corresponding ends terminate adjacent to each other andconnect with the corresponding strut members 508, 510. In an unexpandedconfiguration, the first segment generally cradles the second segment.

An expansion force may be supplied by a balloon member for a balloonexpandable stent and through the removal of a sheath for a selfexpanding stent as is generally known in the art, which causes expansionof the stent. The second segment 504 of the arcuate structure hasbimodal stability such that it exists in one mode prior to expansion,and changes to a second mode after expansion, shown in FIG. 2H. The modeshift is characterized by the foci 512 of the second segment radiuseverting from one side of the second segment to the other. The modeshift results in an increase of the internal area 506 and the radius ofthe first segment 502. The increased radius of the first segment 502corresponds to an increase in the angle 514 defined between thecorresponding strut members thereby resulting in an increased stentdiameter after the expansion force is removed.

Reversal of the second segment 504 to the first stable mode is possiblewhen adequate compressive loading is applied to the stent structure, andthis compressive loading is preferably higher than the load supplied bythe in vivo anatomy.

Further, it is notable that the mechanism of expansion described in thisalternative embodiment does not rely upon plastic deformation of thestent material, making it suitable for fabrication from stent materialssuch as bioabsorbable polymers.

In an alternative embodiment shown in FIG. 21, the strut members mayinclude generally opposed projections 552, 554 located on facingsurfaces of the strut members. The opposed projections 552, 554 aredesigned to move relative to each other during expansion of theendoprosthesis structure, thereby allowing expansion of theendoprosthesis to a larger diameter. The expansion force is preferablysupplied by a balloon element as is generally known in the art. Duringexpansion, the projections will come into contact thereby providing anormal force against the surface of the other projection.

As shown in FIG. 2J, the endoprosthesis is designed to expand to adiameter large enough to allow the apex of a first projection 552 topass beyond the apex of the second projection 554. As the apices passeach other, the contact between the projections ceases, and the apex ofthe first projection 552 is able to move beyond the apex of the secondprojection 554.

Referring now to FIG. 2K, upon removal of the expansion force, therecoil path of the first projection 552 apex causes it to contact asecond side of the second projection 554. The contact between the twoprojections interferes with the relative movement of the projections552, 554 thereby resisting recoil of the overall stent structure andresulting in the angle 556 defined between the strut members beinglarger in the expanded position than in the unexpanded position. Thesurfaces of the projections may be modified to increase frictionalforces between the projections during contact, thereby resisting recoil.Additionally, it is contemplated that features, such as notches andlatches which interact with each other to “lock” the two projectionstogether when the stent is in an expanded state.

Further, it is notable that the mechanism of expansion described in thisalternative embodiment does not rely upon plastic deformation of thestent material, making it suitable for fabrication from stent materialssuch as bioabsorbable polymers.

Additional variations of the foot extension are also contemplated. Forexample, the heel portion of the foot extension can extend in acircumferential direction opposite from the toe, but preferably by adistance less than the distance over which the toe extends in the firstdirection.

Any suitable number of foot extensions can be provided on an annularelement in accordance with the present invention. A single footextension can be provided on an annular element if desired. As shown inthe embodiment of FIG. 1 a, however, it is preferable to define aplurality of apices of an annular element with foot extensions 40,wherein each foot extension extends between a pair 9 ofcircumferentially-adjacent strut members. The foot extensions can beprovided on both longitudinal sides 12, 14 of the annular element 10 asshown in FIG. 1 a, or only on a single side of an annular element asshown in FIG. 8. Additionally, and as further shown in FIG. 8, it ispossible to combine an annular element having one or more footextensions with another annular element having no foot extension ifdesired. The plurality of foot extensions, if provided, can all extendin the same circumferential direction, or in opposite circumferentialdirections if desired. For example, and as shown in FIG. 1 a, the footextensions on one longitudinal side of each annular element can extendin one direction circumferentially 17, whereas the foot extensions onthe other side of the annular element extend in the oppositecircumferential direction. In other embodiments, such as FIG. 6, allfoot extensions 40 can extend in the same circumferential direction,either clockwise or counterclockwise when viewed from one end of theendoprosthesis, regardless of the longitudinal side 12, 14 of theannular elements 10 on which the foot extensions 40 are disposed.

When a plurality of foot extensions are provided on an annular element,the foot extensions can be evenly spaced along the corresponding side ofthe annular element as shown in FIG. la, or can be spaced in a staggeredfashion as shown in FIG. 4. The number of apices that are not defined bya foot extension along the corresponding side of the annular element,and thus disposed between foot extensions, will depend upon the totalnumber of apices desired for the annular element and the total number ofsuch apices to be defined by a foot extension.

Further in accordance with the present invention, and as previouslynoted when a plurality of annular elements is provided, the firstannular element and the second annular element are connected to eachother at a connection location. A single connection location can beprovided between two adjacent annular elements, or a plurality ofconnection locations can be provided as preferred. Furthermore, and asdescribed below, the connection location can include one or moreconnectors extending between adjacent annular elements, or theconnection location can be defined by an overlapping geometric patternof two adjacent annular elements.

Preferably, the connection location includes a foot extension. Aspreviously noted, each foot extension defines at least two areas offlexure. Such areas of flexure generally are located in the ankle, toeor heel portions of the foot extension. As such, the foot extension canfacilitate greater longitudinal flexibility when included at theconnection location between two adjacent annular elements. The multipleareas of flexure of the foot extension can also compensate forforeshortening when disposed at the connection location. As the annularelement is expanded, the foot extension can be configured to open in amanner to adjust or compensate for some or all of the change that occursin the longitudinal dimension of the annular element. That is, the footextension can be configured to have a first longitudinal dimension whenin the delivery configuration, and to straighten or retract, as deemednecessary, so as to have a second longitudinal dimension when in thedeployed configuration. The difference between the first longitudinaldimension and the second longitudinal dimension of the foot extensionpreferably is substantially equivalent to the corresponding change inthe longitudinal dimension of the annular element. Similarly, the footextension can be stiffened by increasing the width of one or both of thefirst and second foot portions, or by otherwise altering the geometry ofthe foot extension in a suitable manner, to reduce the amount in whichthe foot extension opens, and thus reduce the extent of relatedforeshortening that occurs at the connection location.

Additionally, when located on a corresponding side betweenlongitudinally-adjacent annular elements, the foot extension of oneannular element includes a base portion generally facing the otherannular element. The base portion provides an elongated region in whicha connection location can be disposed, thus increasing versatility fordesign alternatives. For example, one alternative for increasingcoverage provided by a stent is to configure corresponding zig-zag orsinusoidal patterns of longitudinally-adjacent annular elements lessthan 180 degrees out of phase with each other. That is, with the firstside of a first annular element longitudinally adjacent the second sideof a second annular element, it can be desirable for the apicesproximate the first side of the first annular element to becircumferentially out of alignment with the apices proximate the secondside of the second annular element. The foot extensions of the presentinvention allow such circumferential offset between longitudinallyadjacent apices, even without the use of a connector. The foot extensionof the present invention therefore enables greater axial flexibility,foreshortening compensation, radial expansion and coverage of theendoprosthesis.

The embodiment of FIG. 3, shown substantially in a deliveryconfiguration, includes a plurality of annular elements 10, wherein eachlongitudinal side of an annular element has sixteen (16) apices. In thisembodiment, four apices on a selected side, e.g. twelve (12), ofadjacent annular elements 10 are defined by a foot extension 40, whereinthe foot extensions 40 extend in the same longitudinal direction but inalternate circumferential directions from one annular element 10 to thenext. Each foot extension 40 is configured substantially similar to thatof FIG. 2 c, wherein the base portion 46 is contoured to include firstand second portions. The contoured pattern of the base portion 46 ofeach foot extension 40 overlaps with the pattern of an apex 30 of thecircumferentially-adjacent annular element. Hence, four connectionlocations 50 are provided between longitudinally-adjacent annularelements 10, with three apices 30 disposed between the connectionlocations 50 along the corresponding longitudinal side 12, 14 of eachannular element 10. The annular element 10 at the longitudinal end 102of the endoprosthesis 100 in which the foot extensions 40 are directedis free of foot extensions 40. FIG. 4 shows an alternative embodimentsimilar to that of FIG. 3, wherein the lengths of the strut members 20disposed circumferentially between the foot extensions 40 are varied toreduce the gap area defined between longitudinally-adjacent annularelements 10, and thus increase coverage.

FIG. 5 shows an alternative embodiment similar to that of FIG. 3,wherein the center apex disposed along the longitudinal side 12, betweenthe foot extensions 40 b that define connection locations is defined asa foot extension 40 a. In this manner, circumferentially-adjacent footextensions 40 along a longitudinal side of an annular element areseparated by single apex 30, wherein every other foot extension 40 bforms a connection location with an apex 30 of a longitudinally-adjacentannular element 10. FIG. 6 shows an enlarged detail of an embodimentsimilar to FIG. 5, in the delivery configuration, wherein the baseportion 46 of each foot extension 40 has an increased average width aspreviously discussed with regard to FIG. 2 c. Particularly, the baseportion 46 of each foot extension 40 is contoured with a generallyV-shape to include a first portion 46′ and second portion 46Δ. Thesecond portion 46Δ proximate the toe portion has a width greater thanthe first portion 46′ as previously discussed. Furthermore, the footextensions 40 of FIG. 6 are all directed in the same circumferentialdirection.

FIG. 7 shows an embodiment similar to that of FIG. 3; however, eachannular element includes additional strut members and apices.Particularly, the embodiment of FIG. 7 includes 20 apices, rather than16 apices, on each side of each annular element 10, with every otherapex defined by a foot extension 40. Hence, five connection locations 50are defined between adjacent annular elements 10. The embodiments ofFIGS. 8 and 9 are similar to the embodiment of FIG. 7; however, selectedapices 30 s of one annular element are longitudinally aligned to bedisposed between circumferentially adjacent foot extensions 40 of anadjacent annular element. As previously noted, and in accordance withthe invention, the apices on longitudinally adjacent sides of adjacentannular elements 10 can be disposed so as to be circumferentially out ofalignment with each other. Hence, the strut members 20 s that areinterconnected at the apices 30 s disposed between adjacent footextensions 40 of an adjacent annular element, are provided with agreater length than the remaining strut members so as to dispose theapex 30 s generally between the foot extensions 40. In this manner,resulting coverage and scaffolding can be increased. Each of FIGS. 7-9is shown substantially in a delivery configuration.

FIG. 10 discloses an embodiment in a slightly deployed configurationhaving eight apices per side of each annular element 10. Each annularelement 10 is arranged in a diagonal format to define a 360-degree turnof a helical pattern. In this manner, the circumferential end 18 of oneannular element can be joined with the corresponding circumferential end16 of a longitudinally-adjacent element to form a continuous helicalpattern along the length of the endoprosthesis 100. Two apices on oneside of each annular element are defined by foot extensions 40 similarto that of FIG. 2 b. Each foot extension 40 forms an overlapping patternwith the apex 30 on a circumferentially adjacent side of an annularelements 10. As previously noted with regard to FIG. 2 b, the apex 30 acircumferentially adjacent to the foot extension 40 is longitudinallypositioned to substantially contact the toe portion 48 when in thedelivery configuration to increase coverage, as well as to captureballoon material if desired. The embodiment of FIG. 10 also includes aneyelet or tab to incorporate a radiopaque marker 120 at one or both ends102, 104 of the endoprosthesis if desired. Alternative techniques forincorporating radiopaque material are described below.

In accordance with the present invention the endoprosthesis 100 mayfurther include at least one radiopaque marker disposed in an eyeletthat is integrally formed with the endoprosthesis′ pattern. Theradiopaque.marker preferably is formed of a material having greaterradiopacity than that of which the endoprosthesis is constructed of. Ina preferred embodiment, the radiopaque marker is formed according to theprocess described in greater detail below, wherein a first head ispre-formed on one side of the marker through a pre-forming process, thepre-formed marker is then inserted into the eyelet and a second formingprocess is performed to deform the second end of the marker and form asecond head. Wherein the two heads retain the marker within the eyeletwith high confidence. Additionally, the two marker heads create aninterference fit between the marker and the marker housing. Inaccordance with the present invention and with reference to FIGS. 11through 19 the process of adding markers to an endoprosthesis will bedescribed in greater detail below.

Referring now to FIG. 11, there is shown an exemplary embodiment of anendoprosthesis according to the present invention, wherein theendoprosthesis includes at least one marker housing adjacent to one endof the endoprosthesis wherein a marker may be disposed therein. As shownin FIG. 11, the endoprosthesis includes a plurality of strut membershaving first and second ends, wherein at least one pair of adjacentstrut members further include a foot extension as previously described.The foot extension further includes a marker housing 121, wherein themarker housing is configured to retain a marker 120. As shown in FIG.11, the marker housing is attached to an apex 30 on one end 104 of theendoprosthesis and extends from a foot extension 40 on the opposite end102. The marker housing(s) as shown in FIG. 11 are shown extending alongan axis of either the apex or foot extension, though it is contemplatedthat the marker housings may extend from the apex and foot extension atand angle relative to an axis of the apex or foot extension. Markerhousing 121 is designed such that the mechanical properties of the footextension and/or the endoprosthesis are not affected. Alternatively, itis contemplated that the marker housing 121 may be design such that themarker housing 121 functions as a structural member of theendoprosthesis. As shown, the marker housing 121 includes an apertureformed therein, whereby the aperture is formed having a generallycircular shape. Although, the aperture formed in the marker housing isdescribed as being generally circular in shape, it is contemplated thatthe aperture may be formed having other shapes, such as rectangular,square, oval, octagonal, and the like. As shown in FIG. 11, at least onemarker housing may be additionally formed on the opposite side of theendoprosthesis device 100, wherein the second marker housing 121 isconfigured to be in association with one of the apices formed by theplurality of strut members as described previously.

As described above, a marker 120 may be disposed within the aperture ofthe marker housing. The marker may be composed of any material havinggreater radiopacity than the material from which the endoprosthesisdevice 100 is constructed. Examples of suitable material include,stainless steel, gold, silver, cobalt, platinum, iridium, tantalum, andalloys thereof or similar biocompatible materials. It is furthercontemplated that the marker may comprise bioabsorbable materials,wherein the bioabsorbable materials may further include a beneficialagent, wherein the beneficial agent is configured to elute from thebioabsorbable material over a determined period of time or at acontrolled rate. In a preferred embodiment, the marker comprisestantalum and is embodied in the form of a form of a rivet, wherein therivet includes first and second heads and is formed as a generallycylindrical member. It is contemplated that the marker may bemanufactured as a composite, wherein one material may be radiopaque andthe other material may be a beneficial agent. Wherein the beneficialagent may be configured to elute from the marker after implantation ofthe endoprosthesis.

Referring now to FIG. 12 there is shown an exemplary embodiment of arivet in accordance with the present invention. As shown in FIG. 12, therivet 120 includes a first end 120 a and a second end 120 b, whereinfirst head 122 having an enlarged diameter portion is formed on thefirst end through a forming process described in greater detailbelow.The enlarged diameter portion 122 is configured to retain therivet within the aperture of the marker housing 121 prior to theformation of a second head on the second end of the marker as describedbelow to form the rivet.

In a preferred embodiment, the rivets 120 are formed by first cuttinggenerally cylindrical members having pre-determined length from roundstock, wherein the cut portions may then be tumbled to radius and deburrthe cut edges. These cylindrical members are then annealed at about1,950 degrees Fahrenheit for at least about one hour at high vacuum inargon or other inert environment. The annealing process reduces thelikelihood of the formation of cracks or other defects due to theforming process. In a preferred embodiment, the cylindrical members areformed from tantalum wire, wherein the tantalum wire conforms to ASTM F560-9 or similar specification. The rivets are then processed to producethe enlarged diameter portion. In a preferred embodiment, the enlargeddiameter portion is formed on one end of the marker stock by placing thecylindrical member(s) in a holding fixture, wherein an off-center drillpress is advanced until the tip of a forming mandrel contacts thesurface of the marker stock, whereby the off-centered mandrel displacesmaterial radially to form an enlarged diameter portion. The off-centeredmandrel remains in contact with the marker material for a period betweenabout 1 second and 20 seconds, and more preferably between about 4seconds and about 8 seconds. The pre-formed marker head created throughthe process above and illustrated in FIG. 12 should have a diameterbetween about 0.010 inches and about 0.025 inches, more preferablybetween about 0.015 inches and about 0.020 inches. It shall beunderstood that the above times and diameters given above should beconsidered exemplary, in that other times and diameters may be used.Further still, the rivets may be manufactured utilizing other knowntechniques such as injection molding, casting, machining, hydroformingand the like.

It is further contemplated that the marker 120 may be formed withalternative methods, for example, the marker may be integrally formedwith the endoprosthesis device during the initial manufacturing step.Such a process would involve manipulating a tubular member or a sheet ofmaterial from which the endoprosthesis device is constructed from priorto the formation of the endoprosthesis device. For example, if theendoprosthesis were to be formed from a thin-walled tubular member, agroove or other feature may be formed in one of the walls of the tube,wherein a radiopaque material may then be disposed within the groove orfeature. Alternatively, the locations of the marker housing may bepre-formed on the device wherein markers may pre-disposed within themarker housings prior to the manufacture of the endoprosthesis device,which may then be formed according to known methods and those describedherein.

Referring now to FIG. 13, there is shown a marker housing wherein arivet has been disposed within the aperture of the housing, wherein theenlarged diameter portion 122 of the rivet extends beyond the outersurface of the endoprosthesis device 100 and the second end 120 b of therivet has been deformed to form a second enlarged diameter portion asshown. By forming the second enlarged diameter portion adjacent thesecond end 120 b of the rivet, the rivet 120 is retained within themarker housing with a frictional fit and/or a mechanical interference ofthe enlarged diameter portions and the inner and outer walls of theendoprosthesis device. In a preferred embodiment, the second enlargeddiameter portion is formed on the second end of the cylindrical memberby the following process steps. After having formed the first enlargeddiameter portion on the cylindrical member, the pre-formed marker isplaced within an eyelet of the endoprosthesis. The marker is thenpre-set into the eyelet. The marker may be pre-set into the eyelet witha pair of marker seating pliers, the marker seating pliers having a pairof jaws, one jaw having a smooth surface the other having a cavityformed therein. The un-formed side of the marker is received within thecavity of the pliers; force is then applied to the jaws of the pliers toclose the jaws, thereby seating the marker within the eyelet. Thisprocess is repeated until markers have been disposed within all eyelets.It is further contemplated that the pre-formed markers may be insertedinto the eyelets using an automated system.

The eyelet portion of the endoprosthesis is placed into a holdingfixture, wherein the fixture is configured to retain the endoprosthesisin a desired position such that the second head may be formed on thesecond end of the marker. Referring now to FIG. 14, there is shown aside view of the fixture 200 in accordance with the present invention.As shown, the fixture includes a first half 210 and a second half 220,wherein the first half is slidably disposed relative to the second half.The first half further includes an endoprosthesis receiving member 211,as shown in FIG. 15, wherein the receiving member 211 has a diametergenerally equal to an inner diameter of the expanded endoprosthesis. Thereceiving member further includes a bore extending through the receivingmember, the bore aligned perpendicular to an axis extendinglongitudinally through the receiving member. A marker-forming pin 213 isdisposed within the bore, wherein the marker forming pin 213 has aproximal end and a distal end 214, the distal end of the pin having agenerally convex surface. The generally convex surface configured toengage the second end of the marker and form the second head thereon. Alocating pin 212 is disposed in a second bore, the second bore alignedperpendicularly to the first bore and offset from the axis of thereceiving member, wherein the locating pin 212 engages a portion of themarker forming pin 213, thereby locating the pin 213 relative to thereceiving member 211 and the second end of the marker (not shown).

The second half 220 of the fixture 200 is configured to receive andretain the eyelet of the endoprosthesis while the second head is beingformed. As shown in FIG. 14, the second half 220 of the fixture 200includes a receiving member 240. Referring now to FIG. 16, there isshown a partial plan view of the receiving member 240. As shown in FIG.16, the receiving member 240 includes a eyelet shaped cutout 252, theeyelet shaped cutout configured to receive the eyelet portion of theendoprosthesis when the first half of the fixture is slidably movedtoward the second half to form the second head. Additionally, a markerreceiving pin 260 is disposed within a bore of the receiving member 240,wherein the marker receiving pin 260 is axially aligned with the markerforming pin 213 of the receiving member 211.

In use, after having disposed a pre-formed marked into an eyelet of theendoprosthesis, the endoprosthesis is disposed over the receivingmember, wherein the eyelet and second end of the marker is aligned withthe marker forming pin 213. The fixture 200 is then placed into a forceapplying device, and a force is applied to the first half 210 of thefixture, wherein the first half 210 advances toward the second half 220.In an alternative embodiment a hard stop disposed on the second halfwould be configured to limit the travel of the first half beyond adesired distance. In a preferred embodiment, the first half 210 travelsbetween about 0.05 mm and 1.5 mm more preferably between about 0.08 mmand 1 mm after initial contact of the marker forming pin 213 with thesecond end of the marker. As the first half advances to the second half,the marker-forming pin 213 engages the second end of the marker anddeforms the second end, thereby forming the second head on the marker asshown in FIG. 13. In a preferred embodiment, a force between about 5Nand 300N is applied to the fixture 200, and more preferably a forcebetween about ION and 250N. The force is removed from the fixture andthe endoprosthesis is then removed from the receiving member. Thisprocess is repeated until all eyelets contained finished markers. In apreferred embodiment, the finished markers have total height of betweenabout 0.005 inches and about 0.025 inches, and more preferably betweenabout 0.010 inches and about 0.015 inches.

Referring now to FIG. 17 there is shown an alternative embodiment of thereceiving member 240 of the fixture 200 in accordance with the presentinvention. As shown in FIG. 17, the receiving member 340 includes aplurality of eyelet receiving members, a motor and means for translatingthe eyelet receiving members between a first position and a secondposition.

As shown in FIG. 17, the eyelet receiving members 370 are radiallydisposed adjacent to each other and slidable between said first andsecond position. Each eyelet receiving member 370 further includes afirst end and a second end, the second end including a fitting 372, asshown in FIG. 18, wherein the fittings 375 are configured to engage aneyelet of an endoprosthesis. Each eyelet-receiving member is associatedwith a locating pin 380, the locating pin is dispose within an apertureformed in each eyelet receiving member and is disposed perpendicular tothe eyelet receiving member, wherein the locating pins have a first end382 and a second end 381. The second end 382 of each locating pin 380 isreceived within a groove 392 formed in a first surface of a rotatingmember 390. The rotating member 390 is coupled to a motor 395 or otherrotating means, wherein a control module (not shown) is associated withthe motor 395 to control the rotation of the rotating member, andthereby controlling the translation of the eyelet receiving members fromthe first position to the second position.

The process of forming a marker utilizing the alternative embodiment ofthe fixture illustrated in FIG. 14 is similar to that described above,wherein after a marker has been disposed in an eyelet as describedabove, the endoprosthesis is loaded onto the first half of the fixtureas described above, the first half of the fixture is then advancedtoward the second half of the fixture. In response to the advancement ofa first half, a control. signal is generated and transmitted to themotor 395, wherein in response to the control signal, the motor providesrotational translation of the rotating plate 390, thereby translatingthe eyelet receiving members 370 from the first position, wherein thedistal ends of the eyelet receiving members are spaced apart from eachother, as shown in FIG. 18, to a second closed position, wherein thedistal ends 372 of the eyelet receiving members are disposed adjacent toeach other, as shown in FIG. 19. When the eyelet receiving member aredisposed in the second position, the eyelet of the endoprosthesis isthereby retained by the features formed in the distal ends of the eyeletreceiving members, wherein the second head of the marker can then beformed according to the process described above.

It is further contemplated that the rivet as shown in FIG. 12 may beconstructed of multiple pieces which may then be assembled to form asingle member when disposed within a marker housing in accordance withthe present invention. For example, the rivet may comprise upper,middle, and lower pieces, wherein the middle piece includes means toaffix the upper and lower pieces thereto, such as a protrusion extendingfrom each end of the middle piece, wherein the upper and lower piecesinclude an aperture or recessed area configured to receive theprotrusion. Alternatively, a fourth piece may be utilized to affix theupper, middle and lower pieces together to form a marker in accordancewith the present invention.

Although the marker housings are shown and described as being disposedon either end of the endoprosthesis device of the present invention, itis further contemplated that marker housings may be formed anywherealong the length and/or radius of the endoprosthesis device inaccordance with the present invention. Markers disposed anywhere alongthe length of the endoprosthesis may be utilized to denote the locationwhere the physical properties of the endoprosthesis changes, or where adiameter change occurs, or the location of a side opening formed in thewall of the tubular member.

In addition to the embodiments shown above in FIGS. 10 through 13, it iscontemplated that the marker housings may be formed within an apex ofone or more strut members or within a portion of the foot extension ofthe embodiments shown and described herein. Additionally, it iscontemplated that a marker housing may be formed anywhere along thelength of the endoprosthesis in accordance with the present invention.For example, it may be desirable to have markers disposed anywhere alongthe length of the endoprosthesis between each end of the endoprosthesis.Therefore, in accordance with the present invention, it is contemplatedthat marker housings may be formed for example in the middle of theendoprosthesis to indicate a specific area or property of theendoprosthesis. As such, markers may be disposed in marker housingsformed within the struts, apices, or foot members of the endoprosthesis,or marker housings such as those shown in FIGS. 10 and 11 maybeintegrated in the endoprosthesis anywhere along the length of theendoprosthesis. Further still, a variety of the marker embodimentsdescribed and shown herein may be utilized in any combination along thelength of an endoprosthesis according to the present invention, whereindifferent marker embodiments may be utilized to mark locations ofinterest.

FIG. 20 is an enlarged view of a connection location similar to that ofFIG. 10, wherein the overlapping geometric pattern of a connectionlocation is schematically depicted for purpose of illustration.Particularly, FIG. 20 shows an annular element having a foot extensionsimilar to that of FIG. 2 a. The pattern of the foot extension 40 balong the base portion 46 is aligned longitudinally to overlap with aportion of the pattern of a circumferentially adjacent annular element10. The resulting configuration of the overlapping pattern defines theconnection location 50 between the two annular elements 10. The amountor extent of overlap between the two patterns can be varied as desired.For example, the patterns can be substantially in tangential contact, orcan be fully overlapping. Additionally, fillets or a similar transitioncan be included to smooth or eliminate any sharp or abrupt edges. It isnoted that the thickness at the juncture defined by the overlappingpatterns need not be, and preferably is not, increased. Rather, theoverlapping pattern refers to the resulting configuration when twoseparate patterns share a common surface or area.

FIGS. 21 a through 21 d show alternative connection locations 50 definedby different degrees of geometrical overlap between adjacent annularelements 10. The connected foot extension 40 b and apex 30 of FIG. 21 ahave a slight geometrical overlap, such as a tangential surface contact.FIG. 21 b shows an overlapping pattern, wherein the connected apex 30and foot extension 40 b fully overlap to substantially share a commonmember. As depicted, the apex 30 at the connection location 50 extendslongitudinally further than the unconnected apices 30. In FIG. 21 c, theapex 30 at the connection location 50 protrudes into the foot region ofthe corresponding foot extension 40 b. In this embodiment, the footextension 40 b is generally enlarged and rounded at the base portion 46compared to free foot extensions 40 a to stiffen and reinforce theconnection location 50. Additional areas of flexure can be defined bythe contour of this configuration, as compared to that of the other footextensions. By contrast, connected foot extension 40 b of FIG. 21 dincludes a flattened base portion 46 substantially perpendicular to thelongitudinal axis to define a more relaxed configuration. As with FIG.21 c, the connected apex 30 of this embodiment overlaps with the footextension 40 b and protrudes into the foot region 49.

As noted above, the various aspects of the present invention allow for avariety of different endoprosthesis embodiments, based upon selectivecombinations of the features previously described and shown. Similarly,the endoprosthesis of the present invention can be made using any of anumber of known manufacturing techniques and materials.

The material of construction is preferably selected according to theperformance and biological characteristics desired. For example, theendoprosthesis of the invention can be made to be expanded by the changeof a delivery condition, such as by the removal of a restraint orexposure to the environment within the body lumen, so as to be selfexpanding, or by the application of an external force or energy, such asby a balloon or by a radio frequency. For purpose of illustration andnot limitation, reference is made generally to “self-expanding”embodiments and “balloon expandable” embodiments of the endoprosthesisof the present invention.

Self-expanding embodiments can be made from any of a variety of knownsuitable materials including super elastic or shape memory materials,such as nickel-titanium (NiTi) alloys, Elgiloy, and suitable polymers,such as suitable shape memory polyurethane copolymers, or anyequivalents thereof. An endoprosthesis made of a suitable super elasticmaterial can be compressed or restrained in its delivery configurationon a delivery device using a sheath or similar restraint, and thendeployed to its deployed configuration at a desired location by removalof the restraint as is known in the art. An endoprosthesis made of shapememory material generally can be delivered in a like manner, and ifthermally sensitive, can be deployed by exposure of the endoprosthesisto a sufficient temperature to facilitate expansion as is known in theart. It also is possible to make the self-expanding embodiment of abiocompatible material capable of expansion upon exposure to theenvironment within the body lumen, such as a suitable hydrogel orhydrophilic polymer, including biodegradable or bioabsorbable polymers,such as polycaprolactone (PCL), poly-D,L-lactic acid, Poly-L-lacticacid, poly (lactide-co-glycolide), poly(hydroxybutyrate),polyanhydrides, poly(glycolic acid). For example, if made of anexpandable hydrophilic material, the endoprosthesis can be delivered tothe desired location in an isolated state, and then exposed to theaqueous environment of the body lumen to facilitate expansion.Alternative known delivery devices and techniques for a self-expandingendoprosthesis likewise can be used. Prior to crimping of theself-expanding endoprosthesis for loading into a delivery system, theendoprosthesis may be coated with a lubricant such as silicone oil toreduce force between the endoprosthesis and the crimping device andadditionally to reduce forces of disposing the endoprosthesis in adelivery device. Additionally, the lubricant may reduce deployment forcethereby increasing accuracy of endoprosthesis placement within apatient. The lubricant may be introduced prior to, during, or after thecrimping or loading process.

It is further contemplated that the markers in accordance with thepresent invention may improve the deliverability of a self-expandingendoprosthesis when used with a movable sheath delivery system. Themarkers projecting above the outer surface of the tubular body of theendoprosthesis contact the sheath of the delivery system and hold thesheath above the surface of the endoprosthesis, thereby reducingfriction between the sheath and the endoprosthesis. Additionally, byhaving point contact between the sheath and the endoprosthesis it ispossible the system may be more flexible and thus have better deliverycharacteristics compared to a similar system where the sheath is incontinuous contact with the endoprosthesis. In addition to providingimproved deliverability, it is contemplated that by having the markersprotrude about the surface of the endoprosthesis this may provide lesstrauma to the tissue surrounding the endoprosthesis after delivery ofthe endoprosthesis by holding the surface of the endoprosthesis off thetissue and providing only points of contact.

Balloon expandable embodiments or the like can be made of any of avariety of known suitable deformable materials, including stainlesssteel, silver, platinum, cobalt chromium alloys such as L605, MP35N orMP20N or any equivalents thereof. “L605” is understood to be a tradename for an alloy available from UTI Corporation of Collegeville,Pennsylvania, including about 53% cobalt, 20% chromium and 10% nickel.“MP35N” and “MP20N” are understood to be trade names for alloys ofcobalt, nickel, chromium and molybdenum available from Standard PressSteel Co., Jenkintown, PA. MP35N generally includes about 35% cobalt,35% nickel, 20% chromium, and 10% molybdenum. MP20N generally includesabout 50% cobalt, 20% nickel, 20% chromium and 10% molybdenum. Fordelivery, the endoprosthesis of a suitable material is mounted in thedelivery configuration on a balloon or similar expandable member of adelivery device. Once properly positioned within the body lumen at adesired location, the expandable member is expanded to expand theendoprosthesis to its deployed configuration as is known in the art.Additionally, or alternatively, balloon expandable embodiments can bemade of suitable biocompatible polymers, including biodegradable orbioabsorbable materials, which are either plastically deformable orcapable of being set in the deployed configuration. If plasticallydeformable, the material is selected to allow the endoprosthesis to beexpanded in a similar manner using an expandable member so as to havesufficient radial strength and scaffolding and also to minimize recoilonce expanded. If the polymer must be set in the deployed configuration,the expandable member can be provided with a heat source or infusionports to provide the required catalyst to set or cure the polymer.Alternative known delivery devices and techniques for a self-expandingendoprosthesis likewise can be used.

Additional materials or compounds also can be incorporated into or onthe endoprosthesis if desired. For example, the endoprosthesis can beprovided with one or more coatings of biocompatible material to enhancethe biocompatibility of the device. Such coatings can include hydrogels,hydrophilic and/or hydrophobic compounds, and polypeptides, proteins oramino acids or the like, including poly vinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), parylene, and heparin. A preferred coating materialincludes phosphorylcholine, as disclosed in U.S. Pat. Nos. 5,705,583 and6,090,901 to Bowers et al. and U.S. Pat. No. 6,083,257 to Taylor et al.,each of which is incorporated by reference herein. Such coatings canalso be provided on the endoprosthesis to facilitate the loading ordelivery of beneficial agents or drugs, such as therapeutic agents,pharmaceuticals and radiation therapies. Alternatively, the surface ofthe endoprosthesis can be porous or include one or more reservoirs orcavities formed therein to retain beneficial agent or drug therein as isknown in the art. For purposes of illustration and not limitation, thedrug or beneficial agent can include antithrombotics, anticoagulants,antiplatelet agents, thrombolytics, antiproliferatives,anti-inflammatories, agents that inhibit hyperplasia, inhibitors ofsmooth muscle proliferation, antibiotics, growth factor inhibitors, orcell adhesion inhibitors, as well as antineoplastics, antimitotics,antifibrins, antioxidants, agents that promote endothelial cellrecovery, antiallergic substances, radiopaque agents, viral vectors,antisense compounds, oligionucleotides, cell permeation enhancers, andcombinations thereof.

The endoprosthesis can also be provided with coverings, such as PTFE,ePTFE, Dacron, woven materials, cut filaments, porous membranes,harvested vessels and/or arteries, or others such materials to form astent graft prosthesis. Similarly, a medical device, such as a valve, aflow regulator or monitor device, can be attached to the endoprosthesis,such that the endoprosthesis functions as an anchor for the medicaldevice within the body lumen.

Additionally, an imaging compound or radiopaque material can beincorporated with the endoprosthesis. For example, one or more of theannular elements of the endoprosthesis can be made of a suitableradiopaque material, such as gold, tantalum or a similar material.Alternatively, the radiopaque material can be applied on selectedsurfaces of one or more of the annular elements using any of a varietyof known techniques, including cladding, bonding, adhesion, fusion,deposition or the like. In a preferred embodiment, the material used forfabrication of the endoprosthesis includes a composite structure havingmultilayers of different materials or compositions. Generally, at leastone layer is a base material such as stainless steel, nickel-titaniumalloy or cobalt chromium alloy to impart the intended structuralcharacteristic of the endoprosthesis, and at least another layer is aradiopaque material such as gold or tantalum for imaging purposes. Forexample, a tri-layer structure of 316L-Ta-316L is preferred for aballoon expandable stent and a tri-layer structure of NiTi-Ta-NiTi ispreferred for a self-expanding stent. Suitable multi-layered compositestructures are available in sheet or tube form from UTI Corporation ofCollegeville, Pennsylvania, and are disclosed in U.S. Pat. No.5,858,556, which is incorporated herein by reference. In yet anotherembodiment, one or more marker elements of radiopaque material can beattached to the endoprosthesis. For example, and as previously shown inFIG. 2 g and 2 h, eyelets or tabs can be provided on one or more annularelements, preferably at at least a distal or proximal longitudinal endof the endoprosthesis. A rivet or bead of radiopaque material can thenbe attached to the eyelet or tab in a manner as known in the art.Alternatively, the separate marker can be attached directly to annularelement. For example, and in accordance with a preferred embodiment ofthe invention as shown in FIGS. 1 and 15, a wire or strip of radiopaquematerial can be wrapped around and secured to a base portion of one ormore foot extensions at one or both longitudinal ends of theendoprosthesis; preferably by providing the foot extension with ageometry to enable limited strain in the base portion of the footextension upon deployment.

A variety of manufacturing techniques are well known and may be used forfabrication of the endoprosthesis of the present invention. For example,and in a preferred embodiment, the endoprosthesis can be formed from ahollow tube of suitable material using a known technique, such as bylaser cutting, milling or chemical etching. The structure ismechanically blasted with a media and then electropolished or otherwisefinished to remove burrs and eliminate sharp edges and contaminates. Anadditional de-scaling process may be performed after electropolishing,wherein the de-scaling process involves the use of an acid bath.Alternatively, the endoprosthesis can be fabricated from a sheet ofsuitable material using a similar cutting, milling or etching technique,and then rolled or bent about a longitudinal axis into the desiredshape. If desired, the lateral edges of the structure can be joinedtogether, such as by welding or bonding, to form a closed tubularstructure, or the lateral edges can remain unattached to form an coiled,rolled sheet or open tubular structure. Conversely, a suitable materialof construction can be applied selectively to a substrate to define thedesired pattern of the endoprosthesis structure, and then the substratecan be removed. Other methods of manufacture also can be used for theendoprosthesis of the present invention, such as by bending toroidalrings or elongate lengths of wire into appropriately shaped members,such as that corresponding to each annular element, and then joining theappropriately shaped members together at connection locations by awelding or bonding technique or the like. If a shape memory material isused, such as a nickel titanium alloy, the fabricated structure can beheat treated on a mandrel or the like using known techniques toestablish the desired endoprosthesis shape and dimensions at apredetermined temperature, e.g. when above austenitic transitiontemperature.

An additional step of passivation may be performed during themanufacturing stage of the endoprosthesis in order to form a homogeneousoxide layer for corrosion resistance. The passivation process may beperformed prior to installation of the markers in accordance with thepresent invention or it may be performed after installation of themarkers. Alternatively, multiple passivation processes may be performed,once prior to insertion of the markers and again after insertion of themarkers.

As originally cut or fabricated, the endoprosthesis can correspond toits delivery configuration or to a deployed configuration or aconfiguration therebetween. In this manner, the endoprosthesis can becrimped or otherwise compressed into its delivery configuration on acorresponding delivery device. In another preferred embodiment, theendoprosthesis is originally fabricated from a tube having a diametercorresponding to the deployed configuration. In this manner, thelongitudinally-free portions of the annular elements (e.g., apices notat a connection location) and circumferentially-free portions (e.g., thetoe portion of the foot extensions) can be maintained within the generalcylindrical shape (e.g., diameter) of the endoprosthesis when deployed,so as to avoid such portions from extending radially inwardly when inthe deployed configuration. The endoprosthesis is therefore designed tomatch the target vessel in which the endoprosthesis is to be deployed.For example a stent will typically be provided with an outer diameter inthe deployed configuration ranging from about 1 mm for neurologicalvessels to about 25 mm for the aorta. Similarly, a stent will typicallybe provided with a length ranging from 5 mm to 300 mm. Variations ofthese dimensions will be understood in the art based upon the intendedapplication or indication for the endoprosthesis.

As previously noted, the geometry of each component of theendoprosthesis, such as the width, thickness, length and shape of thestrut members and foot portions, as well as of the connectors ifprovided, is preferably selected to obtain predetermined expansion,flexibility, foreshortening, coverage scaffolding, and cross profilecharacteristics. For example, longer strut members can promote greaterradial expansion or scaffolding coverage. The phase difference orcircumferential alignment between adjacent annular elements likewise canbe altered to control coverage and flexibility as well as facilitatemore uniform drug delivery. Similarly, the number and placement ofconnection locations and, if present, the connectors, betweenlongitudinally-adjacent annular elements are preferably selected toobtained the desired flexibility of the endoprosthesis. The number ofapices and foot extensions between connection locations also can bevaried to achieve desired performance characteristics. FIG. 22 depicts arepresentative embodiment depicting such variations within anendoprosthesis of strut lengths and strut widths for varied rigidity,and of connector locations for varied flexibility.

As recognized from the detailed description above, the foot extensionsparticularly enhance and provide versatility in the design of theendoprosthesis of the present invention. The foot extension can beconfigured and dimensioned relative to the strut members and theremainder of the endoprosthesis to compensate for longitudinalforeshortening upon stent expansion. For example, the areas of flexureof the foot extensions can be adjusted by contouring the foot geometryand dimensions, as well as by altering the lengths of selected strutmembers. Alternatively, the geometry of the foot extension can beconfigured to provide a desired amount of lengthening or shortening ofthe endoprosthesis upon expansion. The foot extensions can be configuredto balance or assist in evenly distributing strain or expansion of theendoprosthesis. The foot extensions also can improve and control theflexibility of the endoprosthesis, preferably without substantiallyimpacting the desired coverage or scaffolding of the endoprosthesis. Thecircumferentially elongated base portion of each foot extension providesa wide range of connection locations, and allows adjacent annularelements to be attached over a range of phase differences orcircumferential alignment. The foot extensions can be configured toproduce a torque on longitudinally free portions, such as unconnectedapices, to maintain these longitudinally free portions within thegeneral cross profile of the endoprosthesis when flexed along itslongitudinal axis or expanded to its deployed configuration. Thisfeature can be adjusted if it is desired to embed portions of theendoprosthesis into the vessel wall or other tissue.

Reference is now made to two exemplary preferred embodiments of a stentof the present invention; a self-expanding stent as shown in FIGS. 23 athrough 23 f, and a balloon expandable stent as shown in FIGS. 24 athrough 24 f.

FIG. 23 a shows the planar format of a preferred embodiment of aself-expanding stent as cut and polished in a slightly deployedconfiguration. As depicted herein, the self-expanding stent comprisesten annular elements 10 with five connection locations 50 betweenlongitudinally-adjacent annular elements 10 for an approximate stentlength of about 21 mm. Annular elements can be added to increase thestent length, or omitted to decrease the stent length, as desired. Eachannular element 10 includes fifteen apices per longitudinal side. On onelongitudinal side 12 of each annular element 10, five apices are definedby foot extensions 40. Two circumferentially-adjacent apices 30 arelocated between adjacent foot extensions. On the other longitudinal side14 of each annular element 10, no foot extensions are provided. Eachfoot extension 40 has a shape similar to that of FIG. 2 c, as previouslydescribed in detail. Each of the five connection locations 50 betweenadjacent annular elements 10 is defined by a slightly overlappingpattern of the base portion 46 of each foot extension 40 with acorresponding apex 30 of a longitudinally-adjacent annular element in amanner similar to that of FIG. 21 a. In this manner,longitudinally-adjacent apices of adjacent annular elements are out ofcircumferential alignment with each other so as to be less than 180degrees out of phase. Furthermore, connection locations 50 arecircumferentially displaced or offset from one set of annular elementsto the next.

The self-expanding stent of this preferred embodiment is made from asuitable tube stock of nickel-titanium alloy, such as SE508 or SM508,ASTM Standard F2063-00, comprising about 54.5 to about 57% wt. nickeland about 45.5 to about 42.7% wt. titanium, which is commerciallyavailable from Minitubes, Inc. of Grenoble, France. It is recognized,however, that alternative alloy compositions can be used if desired. Forfabrication of a self-expanding stent having a deployed configurationdiameter of about 7 mm to about 8 mm, the tube stock has an outerdiameter of about 0.091 inch and a uniform wall thickness of about 0.010inch. The tube stock is laser cut with the configuration shown in FIG.23 b as a continuous pattern around the circumference of the tube;wherein only the front half of the structure is shown for clarity. Thecut tube is then mechanical blast and sequentially heat treated on aseries of cylindrical mandrels of increasing diameter using knowntechniques to set the desired deployed configuration of the stent whenin an austenitic state as shown in FIG. 23 d. The heat set stent is thenelectropolished using known techniques. The relevant dimensions of thestrut members for this preferred embodiment, after electropolishing,include a nominal strut length of about 0.055 inch, a nominal strutwidth of about 0.004 inches and a generally uniform thickness of about0.008 inches. Regarding each foot extension, after electropolishing, thefirst portion of the foot extension has a width of about 0.005 inch anda length of about 0.013, as measured along its outer edge, and the baseportion of the foot extension includes total length of about 0.033, asmeasured along its outer edge, with a first portion proximate the heelportion having a width of about 0.005 inch and a second portionproximate the toe portion having a width of about 0.007 inch. The strutmember extending from the ankle portion of the foot extension tapersfrom a width of about 0.005 inch at the end proximate the foot extensionto about 0.004 inch at the opposite end, with a length of about 0.059inch. The strut member extending from the heel portion of the footextension tapers from a width of about 0.005 inch at the end proximatethe foot extension to about 0.004 inch at the opposite end, with alength of about 0.068 inch. After polishing, additional cleaning orpreparation may be required.

Once prepared, the self-expanding stent of this embodiment is compressedto a delivery configuration as shown in the front-half view of FIG. 23c, preferably with the strut members generally parallel to thelongitudinal axis of the stent and each other. The stent can then bedelivered using a conventional retractable sheath delivery catheter, asis known in the art. FIGS. 23 d and 23 e show the self-expanding stentof this embodiment in a deployed configuration. For purpose of clarity,only the front half of the stent is shown in FIG. 23 d. As depicted, thestent of this embodiment has been balanced for generally uniformexpansion. FIG. 23 f shows a self-expanding stent of greater length ofthis embodiment deployed in a curved vessel, wherein the apicesproximate the inner radius of the curve generally open less than theapices proximate the outer radius of the curve.

FIG. 24 a shows the planar format of a preferred embodiment of a balloonexpandable stent as cut and polished in a slightly deployedconfiguration. As depicted herein, the balloon expandable stentcomprises fifteen annular elements 10 with two connection locations 50between longitudinally-adjacent annular elements for an approximatestent length of about 18 mm. Annular elements can be added to increasethe stent length, or omitted to decrease the stent length, as desired.Each annular element includes ten apices per longitudinal side. On onelongitudinal side 12 of each annular element 10, two apices are definedby foot extensions 40. Four circumferentially-adjacent apices 30 arelocated between adjacent foot extensions. On the other longitudinal side14 of each annular element 10, no foot extensions are provided. Eachfoot extension 40 has a shape similar to that of FIG. 2 a, as previouslydescribed in detail. Each of the two connection locations 50 betweenadjacent annular elements 10 is defined by an overlapping pattern of thebase portion 46 of each foot extension 40 b with a corresponding apex 30of a longitudinally-adjacent annular element in a manner similar to thatof FIG. 20. In this manner, longitudinally-adjacent apices of adjacentannular elements are out of circumferential alignment with each other soas to be less than 180 degrees out of phase. Furthermore, connectionlocations 50 are circumferentially displaced or offset from one set ofannular elements to the next.

The balloon expandable stent of this preferred embodiment is made from asuitable tube stock of composite material including an inner layer of316L stainless steel, a middle layer of tantalum, and an outer layer of316L stainless steel, which is available from UTI Corporation ofCollegeville, Pennsylvania, and described in U.S. Pat. No. 5,858,556;the entirety of which is hereby incorporated by reference. It isrecognized, however, that alternative material compositions can be usedif desired. For fabrication of a balloon expandable stent having adeployed configuration diameter of about 2.75 mm to about 3.0 mm, thetube stock has an outer diameter of about 0.062 inch and a generallyuniform wall thickness of about 0.004 inch, with the tantalum layerconstituting between about 3% to about 50% of the wall thickness, andmore preferably between about 10% to about 25% of the wall thicknessdepending upon the intended indication. For example, a coronary stent ofthis dimension preferably would have a tantalum layer of between about15% to about 17% of the tube stock thickness. The tube stock is lasercut with the configuration shown in FIG. 24 b as a continuous patternaround the circumference of the tube; only seven annular elements aredepicted for purpose of clarity. The cut tube is then mechanicallyblasted and electropolished using known techniques. The relevantdimensions of the strut members for this preferred embodiment, afterelectropolishing, include a nominal strut length of about 0.036 inches,a nominal strut width of about 0.003 inches and a generally uniformthickness of about 0.003 inches. Regarding each foot extension, afterelectropolishing, the first portion of the foot extension has a width ofabout 0.005 inch and a length of about 0.008 inch, as measured along theouter edge, and the base portion of the foot extension has a width ofabout 0.005 inch and a length of about 0.021 inch as measure along theouter edge. The strut member extending from the ankle portion of thefoot extension tapers from a width of about 0.004 inch at the endproximate the foot extension to about 0.003 inch at the opposite end,with a length of about 0.034 inch. The strut member extending from theheel portion of the foot extension tapers from a width of about 0.005inch at the end proximate the foot extension to about 0.003 inch at theopposite end, with a length of about 0.042 inch. After electropolishing, additional cleaning or preparation may be required.

Once prepared, the balloon expandable stent of this embodiment iscompressed to a delivery configuration as shown in FIG. 24 c, with onlyseven annular elements depicted for purpose of clarity. Preferably, thestrut members are generally parallel to the longitudinal axis of thestent and each other when in the delivery configuration. The stent canthen be delivered using a conventional balloon delivery device, as isknown in the art. Preferably, a portion of balloon material of thedelivery device is captured in the gap defined by the foot extension andthe circumferentially-adjacent strut member. FIGS. 24 d and 24 e showthe balloon expandable stent of this embodiment in a deployedconfiguration; only seven annular elements are depicted for purpose ofclarity. For purpose of clarity, only the front half of the stent isshown in FIG. 24 d. As depicted, the stent of this embodiment has beenbalanced for generally uniform expansion. FIG. 24 f shows the balloonexpandable stent of this embodiment deployed in a curved vessel, whereinthe apices proximate the inner radius of the curve generally open lessthan the apices proximate the outer radius of the curve. It is furthercontemplated that he endoprosthesis may include eyelets or tabs such asthose shown in FIG. 10, wherein the eyelets or tabs may be utilized toretain the endoprosthesis onto a balloon delivery device, wherein theballoon material may be received within the eyelet or tab during thecrimping and/or heat setting process. Further still, a biocompatibleadhesive may be disposed within the eyelet or tab after theendoprosthesis has been crimped onto the balloon delivery device suchthat the adhesive would releasably affix the endoprosthesis to thesurface of the balloon of the balloon delivery device.

While illustrative embodiments of the invention have been disclosedherein, numerous modifications and other embodiments may be devised bythose skilled in the art in accordance with the invention. For example,the various features depicted and described in the embodiments hereincan be altered or combined to obtain desired endoprosthesischaracteristics in accordance with the invention. Therefore, it will beunderstood that the appended claims are intended to cover all suchmodifications and embodiments, which are within the spirit and scope ofthe present invention.

1. A method for inserting a radiopaque marker in an endoprosthesis,comprising: a. fabricating an endoprosthesis having at least one eyeletsized to receive a radiopaque marker therein; b. pre-forming a firsthead on a radiopaque marker member; c. disposing said marker memberwithin an eyelet of the endoprosthesis, wherein said first head projectsabove a surface of the endoprosthesis; and d. forming a second head on asecond end of the marker member, said second head projecting above asecond surface of the endoprosthesis.
 2. The method according to claim1, wherein said pre-forming step comprises placing the marker member ina clamp and using an off-center drill to form said first head.
 3. Themethod according to claim 1, wherein the method of disposing the markerwithin an eyelet further comprises the step of using a pair of pliers toseat the marker within the eyelet.
 4. The method according to claim 3,wherein the pliers have a first jaw and a second jaw, wherein the secondjaw includes a concave surface.
 5. The method according to claim 4,wherein said concave surface is configured to receive said first head ofsaid marker.
 6. The method according to claim 1, wherein the step ofform ing the second head further comprises the steps of; a. insertingsaid endoprothsesis into a fixture having a receiving member andaligning a marker forming pin with the second end of the marker; b.applying a force to the fixture, thereby causing the marker forming pinto deform the second end of the marker and form the second head.
 7. Themethod according to claim 1, wherein the radiopaque marker member isannealed.
 8. The method according to claim 7, wherein after annealingthe marker has a Rockwell hardness between about 20 and
 50. 9. Themethod according to claim 1, wherein the radiopaque marker member isformed of a material selected from the group consisting of tantalum,silver, gold, stainless steel.
 10. An endoprosthesis for delivery in abody lumen comprising: a first set of interconnected strut membersdefining a first annular element, each strut member of the first annularelement including a first end and a second end; and a second set ofinterconnected strut members defining a second annular element, eachstrut member of the second annular element including a first end and asecond end, the first annular element and the second annular elementaligned longitudinally adjacent to each other along a longitudinal axisand connected to each other with a connector at at least one connectionlocation, wherein at least one connector is constructed of abio-absorbable material.
 11. The endoprosthesis of claim 10, furtherincluding a marker housing associated with one of the annular elementsand extending from one of the ends.
 12. The endoprosthesis of claim 11,wherein the marker comprises a rivet.
 13. The endoprosthesis of claim12, wherein the connector further comprises a non-bio-absorbablematerial.
 14. The endoprosthesis of claim 10, wherein the endoprosthesisis fabricated from a material chosen from the group consisting ofnitinol, tantalum, stainless steel, cobalt, a composite material. 15.The endoprosthesis of claim 10, wherein the bio-absorbable connector isconstructed of a material chosen from the group consisting ofPolygycolic acid (PGA), Polyhydroxybutyric acid, PolyL-Lactic acid(PLLA), Polydilactidel glycolide, Polydilactid acid, PolyDLlactide-co-gycolide.
 16. The endoprosthesis of claim 10, wherein one ofthe annular rings further includes at least one foot extension extendingbetween a pair of circumferentially-adjacent strut members.
 17. Theendoprosthesis of claim 16, wherein the foot extension has a first footportion extending circumferentially from a first end of one of thecircumferentially-adjacent strut members and a second foot portionextending circumferentially from a first end of the other of thecircumferentially-adjacent strut members.
 18. The endoprosthesis ofclaim 11, wherein the connector comprises a bio-absorbable component anda metallic component.
 19. The endoprosthesis of claim 17, wherein thefoot extension further includes a modulator member disposed adjacent thefirst foot portion and the second foot portion, the modulator membercoupled to adjacent strut members.
 20. The endoprosthesis of claim 19,wherein the modulator is constructed of a bio-absorbable material chosenfrom the group consisting of Polygycolic acid (PGA), Polyhydroxybutyricacid, PolyL-Lactic acid (PLLA), Polydilactidel glycolide, Polydilactidacid, PolyDL lactide-co-gycolide.